Ceronix 1493 fade to blurr

[Badbaud]

In about 10 minutes the sharp, focused, picture on this 220V 1493 CGA monitor's focus starts to fade to a un-focused picture.

Does anyone know what component(s) would cause this problem?

[cowboygames]

My best guess would be carbon buildup on the guns that feathers as it gets hot

[Badbaud]

The guns were cleaned and all 3 have good emission.

[cowboygames]

Crappy focus block assembly on the flyback maybe? Or the flyback itself...

[Badbaud]

I'm going to try replacing the FBT Monday to see if that works.

I was hoping it was some circuit on the board that caused it, FBT's ain't cheap.

[cowboygames]

Have you tried making adjustments on the focus control while it's having it's issue?
You can also try placing the tube face down on a table and tap on the neck of the tube while it's warm to allow any floatimg pieces of carbon to drop into the bottom of the tube. It's possible to get pieces laying in the neck after a gun cleaning and they travel when the tube warms up

[Badbaud]

I can adjust the FBT and get a sharp picture back but within 10 minutes it starts getting blurry again.

When I "brighten" up the guns with our Sencore tube tester I always tap on the neck with the plastic end of a nut driver, that really helps getting the guns back into the green.

[cowboygames]

That's good practices to do that. Do you also turn the tube on it's face to allow the carbon blown off the guns to fall into the main part of the tube. I had several instances where the rejuvinator blew the carbon off the guns but they floated around inside the neck and caused problems later on. Sometimes letting it get good and hot then rapping on the neck with the handle of a screwdriver, nut driver, whatever will cause the arc you need to blow a carbon short off, IF that's the cause of your current issue. We saw this a LOT on Zenith TV's in the mid 90's but they had a lot of carbon buildup we'd cleaned off. Your situation would depend on how bad it was before you rejuvinated it. It's entirely possible that the guns are failing when they heat up also. S9me of this is just educated guessing too, as you know, unless you're the one running the machine you can't know what shape it was in to start with, but these are things I've seen many times before and what I did to fix, attempt to fix, them. Some aren't fixable unfortunately...

[Badbaud]

That is a valid concern. When I hooked the tube up to the tester all 3 guns were dead with only one red notch per gun.

It took a rejuv of all 3 guns just to get the blue a couple of notches into the green.

The other two guns only produced a couple more red notches and would never go into the green.

The gun tracking test failed also.

But when I hooked up the monitor to our Game King test machine the colors looked passable, then the focus would go south.

[cowboygames]

If the rejuvinating machine is handy, try another rejuv but let the heaters run for about an hour before you zap the guns, tap the heck out of the neck while rejuving each gun and do it all with the tube on it's face if you can. If that doesn't work I would geuss the guns are shot. Like I said above, some just can't be fixed, but from your description it definately sounds like carbon is the cause of the problem. You can try the process a couple times if you're the don't give up type, though you should consider yourself lucky if it works

[Badbaud]

It was the FBT, replaced the FBT and ran the monitor for 4 hours without a blur.

[cowboygames]

Excellent! Congratulations on getting it going